It is often desirable that an object will have a surface that has an increased ability to attract and host the growth, attachment and proliferation of living biological cells. This is often the case for certain biological laboratory wares, including for example, tissue culture dishes, flasks and roller flasks, wells and chamber slides, plates, Petri dishes, etc. It is also often the case for medical objects intended for implant and also for environmental testing devices used to test airborne or waterborne contaminants.
As used herein, the term “bioactivity,” used in relation to a surface or an object or portion of an object, is intended to mean suitability of the surface or object or object portion for attracting living cells and/or tissues, including bone, or fluids thereto, or for improving cell and/or tissue activity thereon, or for attaching living cells thereto, or for promoting growth of living cells thereon, or for promoting proliferation of living cells thereon. Living cells, tissues and fluids include such materials presently or recently alive and extracted from or within a mammal (including human) or synthetic simulations thereof. As used herein the term “titania” is intended to include oxides of titanium in all forms including ceramic forms, and the titanium metal itself (or an alloy thereof) together with a surface coating of native oxide or other oxide comprising the element titanium (including without limitation TiO2, and or TiO2 with imperfect stoichiometry). Implantable medical devices are often fabricated from titanium metal (or alloy) that typically has a titania surface (which may be either a native oxide, or a purposely oxidized surface, or otherwise).
As used herein, the term “drug” is intended to mean a therapeutic agent or a material (including small molecule pharmaceutical drugs and larger biologics) that is active in a generally beneficial way, which can be released or eluted locally in the vicinity of an implantable medical device to facilitate implanting (for example, without limitation, by providing lubrication) the device, or to facilitate (for example, without limitation, through biological or biochemical activity) a favorable medical or physiological outcome of the implantation of the device. The meaning of “drug” is intended to include a mixture of a drug with a polymer that is employed for the purpose of binding or providing coherence to the drug, attaching the drug to the medical device, or for forming a barrier layer to control release or elution of the drug. A drug that has been modified by ion beam irradiation to densify, carbonize or partially carbonize, partially denature, cross-link or partially cross-link, or to at least partially polymerize molecules of the drug is intended to be included in the “drug” definition.
As used herein, the term “intermediate size”, when referring to gas-cluster size or gas-cluster ion size is intended to mean sizes of from N=10 to N=1500. Where N signifies the number of monomers comprising the gas-cluster or gas-cluster ion.
As used herein, the term “monomer” refers equally to either a single atom or a single molecule. The terms “atom,” “molecule,” and “monomer” may be used interchangeably and all refer to the appropriate monomer that is characteristic of the gas under discussion (either a component of a cluster, a component of a cluster ion, or an atom or molecule). For example, a monatomic gas like argon may be referred to in terms of atoms, molecules, or monomers and each of those terms means a single atom. Likewise, in the case of a diatomic gas like nitrogen, it may be referred to in terms of atoms, molecules, or monomers, each term meaning a diatomic molecule. Furthermore a molecular gas like CO2, may be referred to in terms of atoms, molecules, or monomers, each term meaning a three atom molecule, and so forth. These conventions are used to simplify generic discussions of gases and gas-clusters or gas-cluster ions independent of whether they are monatomic, diatomic, or molecular in their gaseous form.
Biological laboratory wares may be employed in cell culture, tissue culture, explant culture, and tissue engineering applications (for examples) and is commonly formed from generally inert and/or biocompatible materials like glass, quartz, plastics and polymers, and certain metals and ceramics. It is often desirable to be able to modify at least a portion of the surface of such biological laboratory wares to enhance their bioactivity.
Medical objects intended for implant into the body or bodily tissues of a mammal (including human), as for example medical prostheses or surgical implants or grafts, may be fabricated from a variety of materials including, but not limited to, various metals, metal alloys, plastic or polymer or co-polymer materials (including, without limitation, woven, knitted, and non-woven polymeric/co-polymeric fabrics and solid materials such as polyether ether ketone (PEEK)), solid resin materials, glass and glassy materials, biological materials such as bone and collagen, silk and other natural fibers, and other materials (including without limitation, poly[glutamic acid], poly[lactic-co-glycolic acid], and poly[L-lactide]) that may be suitable for the application and that are appropriately biocompatible. As examples, certain stainless steel alloys, titanium and titanium alloys (including possible native oxide coatings), cobalt-chrome alloys, cobalt-chrome-molybdenum alloy, tantalum, tantalum alloys, zirconium, zirconium alloys (including possible native oxide coatings), polyethylene and other inert plastics, and various ceramics including titania, alumina, and zirconia ceramics are employed. Polymeric/co-polymeric fabrics may for example be formed from polyesters (including polyethylene terephthalate (PETE)), polytetrafluoroethylene (PTFE), aramid, polyamide or other suitable fibers. Medical objects intended for implant include for example, without limitation, vascular stents, vascular and other grafts, dental implants, artificial and natural joint prostheses, coronary pacemakers, implantable lenses, etc. and components thereof. Often such a device may have a native surface state with cellular adhesion and cellular proliferation properties that are less than ideal for the intended purpose. In such cases it is often desirable to be able to modify at least a portion of the surface of the object to enhance cellular attachment thereto in order to make it more suitable for the implant application.
Environmental testing devices often include materials such as metals, plastics and polymers, glasses and quartz, etc.
During the past decade, gas-cluster ion beams (GCIB) have become well known and widely used for a variety of surface and subsurface processing applications. Because gas-cluster ions typically have a large mass, they tend to travel at relatively low velocities (compared to conventional ions) even when accelerated to substantial energies. These low velocities, combined with the inherently weak binding of the clusters, result in unique surface processing capabilities that lead to reduced surface penetration and reduced surface damage compared to conventional ion beams and diffuse plasmas.
Gas-cluster ion beams have been employed to smooth, etch, clean, form deposits on, or otherwise modify a wide variety of surfaces. Because of the ease of forming GCIBs using argon gas and because of the inert properties of argon, many applications have been developed for processing the surfaces of implantable medical devices such as coronary stents, orthopedic prostheses, and other implantable medical devices using argon gas GCIBs. For example, U.S. Pat. No. 6,676,989C1 of Exogenesis Corporation issued to Kirkpatrick et al. teaches a GCIB processing system having a holder and manipulator suited for processing tubular or cylindrical workpieces such as vascular stents. In another example, U.S. Pat. No. 6,491,800B2 of Exogenesis Corporation issued to Kirkpatrick et al. teaches a GCIB processing system having workpiece holders and manipulators for processing other types of non-planar medical devices, including for example, hip joint prostheses. In still another example, U.S. Pat. No. 7,105,199B2 of Exogenesis Corporation issued to Blinn et al. teaches the use of GCIB processing to improve the adhesion of drug coatings on stents and to modify the elution or release rate of the drug from the coatings.
Gas-cluster ion-beam (GCIB) irradiation has been used for nano-scale modification of surfaces. In the commonly held published US patent publication 2009/0074834A1, “Method and System for Modifying the Wettability Characteristics of a Surface of a Medical Device by the Application of Gas Cluster Ion Beam Technology and Medical Devices Made Thereby,” GCIB irradiation has been shown to modify the hydrophilic properties of non-biological material surfaces. It is generally known that cells, including but not limited to, anchorage-dependent cells such as fibroblasts and osteoblasts prefer hydrophilic surfaces to attach, grow, or differentiate well and they also prefer charged surfaces at physiological pH. Many methods have been employed to increase hydrophilicity or alter charge on non-biological surfaces, such as sandblasting, acid etching, sandblasting plus acid etching (SLA), plasma spraying of coatings, CO2 laser smoothing and various forms of cleaning, including mechanical, ultrasonic, plasma, and chemical cleaning techniques. Other approaches have included the addition of surfactants or the application of films or coatings having different wettability characteristics. Various methods have also been employed to increase cell adherence properties of surfaces such as UV treatment, UV and ozone treatment, covalently attaching polyethylene glycol) (PEG), and the application of protein products such as the antibody anti-CD34 and arginine-glycine-aspartate peptides (RGD peptides).
Ions have long been favored for many processes because their electric charge facilitates their manipulation by electrostatic and magnetic fields. This introduces great flexibility in processing. However, in some applications, often including the processing of drugs, biological materials, and electrically insulating materials the charge that is inherent to any ion (including, but not limited to, charged gas-cluster ions in a GCIB) may in some cases produce undesirable effects in the processed surfaces. GCIB has a distinct advantage over conventional ion beams in that a gas-cluster ion with a single or small multiple charge enables the transport and control of a much larger mass-flow (a cluster may consist of hundreds or thousands of molecules) compared to a conventional ion (a single atom, molecule, or molecular fragment.) Particularly in the case of insulating materials, ion beam processed surfaces often suffer from charge induced damage resulting from abrupt discharge of accumulated charges, or production of damaging electrical field-induced stress in the material (again resulting from accumulated charges.) In such cases, GCIBs have an advantage due to their relatively low charge per mass, but may not entirely eliminate the workpiece-charging problem in many instances. Furthermore, moderate to high current intensity ion beams may suffer from a significant space charge-induced defocusing of the beam that tends to inhibit transmitting a well-focused beam over long distances. Again, because of their lower charge per mass, charged GCIBs have an advantage in this respect, but the space charge transport effects are not fully eliminated.
A further instance of need or opportunity arises from the fact that although the use of beams of neutral molecules or atoms provides benefit in some surface processing applications and in space charge-free beam transport, it has generally not been easy or economical to produce intense beams of neutral molecules or atoms except for the case of jets, where the energies are generally on the order of a few milli-electron-volts per atom or molecule. Higher energies per particle can be beneficial or necessary in many applications, for example when it is desirable to break surface bonds to facilitate cleaning, etching, smoothing, deposition, surface chemistry effects or other surface modification. In such cases, energies of from an eV to a several tens of eV per particle (or even higher) can often be useful. Methods and apparatus for forming such neutral beams by first forming an accelerated charged GCIB and then neutralizing or arranging for neutralization of at least a fraction of the beam and separating the charged and uncharged fractions are disclosed in herein. The neutral beams may consist of neutral gas-clusters, neutral monomers, or combinations of both.
It is therefore an object of this invention to provide a surface and an object having at least a portion of its surface modified by GCIB processing to have improved bioactivity.
It is further an objective of this invention to provide methods of forming a surface or an object having at least a portion of its surface modified to have improved bioactivity by employing GCIB technology.
It is further an objective of this invention to provide methods of forming a surface or an object having at least a portion of its surface modified to have improved bioactivity by employing GCIB technology.
Another objective of this invention is to provide a surface and an object having at least a portion of its surface modified to have improved bioactivity by employing neutral beam technology, wherein the neutral beam comprises gas-clusters, monomers, or a combination of monomers and gas-clusters.
A further objective of this invention is to provide a surface and an object having at least a portion of its surface modified to have improved bioactivity by employing neutral beam technology, wherein the neutral beam comprises gas-clusters, monomers, or a combination of monomers and gas-clusters derived from an accelerated gas-cluster ion beam.
Still another objective of this invention is to provide methods for modifying a surface or at least a portion of a surface of an object with improved bioactivity by employing neutral beam technology, wherein the neutral beam comprises gas-clusters, monomers, or a combination of monomers and gas-clusters.
Yet another objective of this invention is to provide an object for medical implantation having at least a portion of its surface modified by GCIB processing and having cells attached in vitro prior to medical implantation.
A still further objective of this invention is to provide methods of forming an object for medical implantation having at least a portion of its surface modified by GCIB technology and by in vitro attachment of cells prior to medical implantation.